In one such sealing cap, known from German Patent Disclosure DE 197 53 592 A1, the valve arrangement has two valve bodies, of which, in the position of repose, the first valve body rests directly on a sealing seat of an inner cap part under spring loading, and the second valve body is pressed against a further compression spring by the spring-loaded first valve body. The two-stage opening and closing of the flow connections is achieved by providing that the first valve body is lifted by means of the second valve body from its sealing seat on the inner cap part if the first limit value is exceeded; that when the second limit value is reached, the second valve body presses against a further sealing seat of the inner cap part and thus closes the first flow connection again; and that for the safety stage, an intermediate valve body disposed between the first and second valve bodies lifts with its sealing seat from a sealing face of the second valve body.
In terms of its valve arrangement, a sealing cap of this kind is complicated structurally, in terms of production, and in terms of assembly because of the many components.
From German Patent DE 41 07 525 C1, a sealing cap is also known that provides for a two-stage pressure equalization of the close container that may become necessary. In this sealing cap, the valve arrangement also has two valve bodies, which are internested in one another; the second valve body is pressed against a sealing seat on the inner cap part by the spring loading of the first valve body. In this arrangement, when the first limit value of the internal container pressure is exceeded, the second valve body lifts, carrying the first valve body with it, from its sealing seat on the inner cap part, and when the second limit value is reached presses against an opposed sealing face of the inner cap part again. In the safety stage, the first valve body is lifted from the second valve body.
In the valve arrangement of this known sealing cap, the same disadvantages arise as in the sealing cap described earlier above, and furthermore there is the problem that the sealing seats and sealing faces of the two valve bodies and of the inner cap part, along with the axial travel of the second valve body, must be adapted to one another within narrow tolerances.
From German Patent Disclosure DE 197 32 885 A1, a sealing cap with safety locking for openings of containers is also known. This safety locking makes it possible, when overpressure prevails in the container, to prevent the sealing cap from coming unscrewed, specifically by providing that the sealing cap is blocked nonrotatably relative to the fill nozzle on the container. This known safety locking uses an axially movable insert, which surrounds the inner cap part or its valve arrangement and is as a result exposed directly to the overpressure prevailing in the container, because its inner bottom is located in the opening of the fill nozzle. This axially movable insert is axially movable but is retained nonrotatably in a tubular supplementary inner part which is seated nonrotatably in the fill nozzle of the container and relative to which the sealing cap is rotatable. When overpressure occurs in the container, the insert is moved axially in the direction of the sealing cap and engages it nonrotatably. The result is a blockage of rotation of the sealing cap via the insert and the supplementary inner part with the fill opening of the container.
The provisions in this reference for torsion prevention or safety locking are complicated both structurally and because of the number of components to be used. Moreover, the axially movable insert and the tubular supplementary inner part not only increase the diameter of the inner cap part of the sealing cap but also reduce the effective area of the valve arrangement of the sealing cap, with adverse effects on the response behavior of the valve arrangement.